1. Technical Field of the Invention
The present invention relates to stators for electric rotating machines that are used in, for example, motor vehicles as electric motors and electric generators.
2. Description of the Related Art
Japanese Patent Application Publication No. H11-341730 discloses an automotive alternator which includes a rotor and a stator. The stator includes a hollow cylindrical stator core, which is disposed to surround the rotor, and a stator coil mounted on the stator core. The stator coil is formed of a plurality of electric conductor segments. Each of the electric conductor segments includes inside portions that are received in corresponding slots of the stator core and outside portions that protrude outside the corresponding slots. Moreover, each corresponding pair of the electric conductor segments are joined together by welding corresponding ends of the outside portions of the electric conductor segments on one axial side of the stator core, forming a joint (or weld) therebetween. The joints formed between the electric conductor segments are spaced from one another so as to together form an annular shape. Furthermore, insulators, which are made of an electrically insulative resin, are formed to each cover one of the joints formed between the electric conductor segments, thereby electrically insulating the joints from one another and from other components of the alternator located close to the joints.
With the above configuration, to more reliably ensure the electric insulation between the joints, it is necessary to perform a fail-safe design so that even if the insulators become peeled from the joints, it is still possible to prevent a short circuit from occurring between the joints.
More specifically, when the insulators are peeled from the joints, an electrically conductive path may be formed between an adjacent pair of the joints along the surfaces of insulating coats that cover the electric conductor segments, thereby causing a short circuit to occur therebetween. Therefore, to more reliably ensure the electric insulation between the joints, it is necessary to secure a sufficiently long creepage distance for each adjacent pair of the joints with respect to the voltage to be applied to the stator coil. Here, for each adjacent pair of the joints, the creepage distance denotes the shortest distance between the pair of the joints along the surfaces of the insulating coats covering the electric conductor segments.